The present invention generally relates to refrigeration systems and, more particularly, to refrigeration systems having flow-control restriction or expansion devices incorporated therein.
A refrigeration system, such as a motor vehicle air conditioner, typically has a closed circuit through which a refrigerant undergoes a thermodynamic cycle. The circuit of a motor vehicle air conditioner typically includes an engine driven semi-hermetic compressor, a condenser connected in series to the compressor, a flow-control restriction or expansion device, which is often referred to as a flow-control valve or expansion valve, connected in series to the condenser, and an evaporator connected in series between the expansion device and the compressor. The compressor raises the pressure ofxe2x80x9clow-pressurexe2x80x9d gaseous refrigerant to a pressure suitable for operation of the condenser. xe2x80x9cHigh-pressure hotxe2x80x9d gaseous refrigerant passes from the compressor to the condenser. The condenser condenses the high-pressure hot refrigerant by transferring heat from the refrigerant to the ambient environment or atmosphere located outside the motor vehicle. The expansion device causes the high-pressure liquid refrigerant exiting the condenser to experience a sudden pressure drop, causing the liquid refrigerant to cool and expand (usually a constant enthalpy process). The xe2x80x9clow-pressure coldxe2x80x9d liquid refrigerant passes to the evaporator where it vaporizes by absorbing heat from surrounding air and as a result cools the surrounding air. Typically, a fan or blower forces air across the evaporator and delivers xe2x80x9ccooledxe2x80x9d air to a passenger compartment of the motor vehicle. Low-pressure hot gaseous refrigerant exits the evaporator and returns to the compressor and the above-described thermodynamic cycle repeats as the refrigerant flows through the circuit.
Such motor vehicle air conditioning systems can be easily tailored for efficient cooling at specific driving conditions such as, for example, highway driving (constant speed) or city driving (stop and go). When tailored for efficient cooling at one driving condition, however, cooling efficiency can be less than desirable while at other driving conditions. One solution has been to incorporate an expansion valve operable between different flow conditions. For example, U.S. Pat. No. 5,715,704 to Cholkeri et al., which is expressly incorporated herein in its entirety by reference, discloses an electronically-controlled expansion valve which operates in two different flow conditions. The expansion valve is a high/low stage direct controlled solenoid valve. The solenoid operates the expansion valve between a high-flow state providing high or maximum refrigerant flow through the expansion valve and a low-flow state providing low or minimum refrigerant flow through the expansion valve. The solenoid is periodically energized to obtain the low-flow state and de-energized to obtain the high-flow state in response to refrigeration system parameters and/or motor vehicle parameters such as, for example, head pressure, vehicle speed and engine rpm to provide more efficient cooling at various driving conditions.
While refrigeration systems with such expansion valves are effective at providing more efficient cooling at multiple driving conditions, it is desirable to have additional refrigerant flow rates to provide even more efficient operation. Accordingly, there is a need in the art for an improved refrigeration system having a flow-control valve with more than two flow rates.
The present invention provides a refrigerant flow-control valve operable between a mid-flow condition, a low-flow condition, and a high-flow condition which overcomes at least some of the above-noted problems of the related art. According to the present invention, the refrigerant flow-control valve includes a body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has first, second, and third restrictions and first and second valve-element flow passages which are adapted such that refrigerant flows through the first valve-element flow passage generally in parallel with the second restriction, refrigerant flows through the second valve-element passage generally in parallel with the third restriction, and refrigerant flows through the first restriction generally in series with the first valve-element flow passage and the second restriction and generally in series with the second valve-element flow passage and the third restriction. A first valve element is located within the body and is movable between a first position closing the first valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the first valve-element flow passage to permit refrigerant flow therethrough. A first biasing member located within the body resiliently urges the first valve element into the second position. A second valve element is located within the body and is movable between a first position closing the second valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the second valve-element flow passage to permit refrigerant flow therethrough. A second biasing member located within the body resiliently urges the second valve element into the first position. Constructed in this manner, the first biasing member is preferably adapted to maintain the first valve member in the second position except when a control signal is sent to a valve actuator to overcome the bias of the first biasing member to selectively move the first valve element to the second position. The second biasing member is preferably adapted to maintain the second valve member in the first position except when a predetermined pressure drop across the valve overcomes the bias of the second biasing member to automatically move the second valve element to the first position with fluid pressure.
According to another aspect of the present invention, the present invention provides a refrigerant flow-control valve operable between a mid-flow condition, a low-flow condition, and a high-flow condition The flow-control valve includes a tubular-shaped body having an inlet and an. outlet and forming a refrigerant passageway extending from the inlet to the outlet, a cylindrically-shaped restrictor secured within the tube and forming a first restriction, a cylindrically shaped end stop secured within the tube and spaced-apart from the restrictor, and a plunger within the tube at least partially between the restrictor and the end stop. The plunger forms a first valve-element flow passage between the plunger and the tube. The plunger carries a first valve element and is movable between a first position closing the first valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the first valve-element flow passage to permit refrigerant flow therethrough. The plunger forms a second restriction generally connected in parallel with the first valve-element flow passage and generally connected in series with the first restriction. The second restriction has a greater resistance to refrigerant flow than the first restriction. A first biasing member is within the tube and resiliently urges the first valve element into the second position. A valve actuator is adapted to selectively move the first valve element to the first position in response to a control signal supplied thereto. The valve also includes a cylindrically-shaped collar secured within the tube and forms a second valve-element flow passage. The collar is spaced-apart from the restrictor. A poppet is within the tube at least partially between the restrictor and the collar and carries a second valve element. The poppet is movable between a first position closing the second valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the second valve-element flow passage to permit refrigerant flow therethrough. The poppet forms a third restriction generally connected in parallel with the second valve-element flow passage and is generally connected in series with the first restriction. The third restriction has a greater resistance to refrigerant flow than the first restriction and a lesser resistance to refrigerant flow than the second restriction. A second biasing member is within the tube and resiliently urges the second valve element into the first position. The poppet is adapted to automatically move the second valve element to the second position in response to a pressure head across the flow-control valve.
According to yet another aspect of the present invention, the present invention provides a refrigeration system. The refrigeration system has a compressor, a condenser, and a evaporator connected in series and an expansion valve connected in series between the condenser and the evaporator. The refrigeration system includes a body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has first, second, and third restrictions and first and second valve-element flow passages which are adapted such that refrigerant flows through the first valve-element flow passage generally in parallel with the second restriction, refrigerant flows through the second valve-element passage generally in parallel with the third restriction, and refrigerant flows through the first restriction generally in series with the first valve-element flow passage and the second restriction and generally in series with the second valve-element flow passage and the third restriction. A first valve element is located within the body and is movable between a first position closing the first valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the first valve-element flow passage to permit refrigerant flow therethrough. A first biasing member located within the body resiliently urges the first valve element into the second position. A second valve element is located within the body and is movable between a first position closing the second valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the second value-element flow passage to permit refrigerant flow therethrough. A second biasing member located within the body resiliently urges the second valve element into the first position. Constructed in this manner, the first biasing member is preferably adapted to maintain the first valve member in the second position except when a control signal is sent to a valve actuator to overcome the bias of the first biasing member to selectively move the first valve element to the second position. The second biasing member is preferably adapted to maintain the second valve member in the first position except when a predetermined pressure drop across the valve overcomes the bias of the second biasing member to selectively move the second valve element to the first position with fluid pressure.
According to yet even another aspect of the present invention, the present invention provides a method of delivering refrigerant from a high pressure region to a low pressure region of a refrigeration system through a variable dimension passageway to expands the refrigerant as it enters the low pressure region. The method includes the step of coupling the high and low pressure regions through a valve body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has first, second and third restrictions and first and second valve-element flow passages adapted such that refrigerant flows through the first valve-element flow passage generally in parallel with the second restriction, refrigerant flows through the second valve-element flow passage in parallel with the third restriction, and refrigerant flows through the first restriction generally in series with the first valve-element flow passage and the second restriction and generally in series with the second valve-element flow passage and the third restriction. A first valve element is mounted within the valve body such that the first valve element is movable between a first position closing the first valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the first valve-element flow passage to permit refrigerant flow therethrough. The first valve element is resiliently biased into the second position and is selectively moved to the first position in response to a control signal supplied thereto. A second valve element is mounted within the valve body such that the second valve element is movable between a first position closing the second valve-element flow passage to generally prevent refrigerant flow therethrough and a second position opening the second valve-element flow passage to permit refrigerant flow therethrough. The second valve element is biased into the first position and is automatically moved to the second position in response to a predetermined fluid pressure acting against the bias at a predetermined xe2x80x9cblow-offxe2x80x9d pressure.